dom/tests/mochitest/general/test_performance_now.html@b8a032363ba2 (annotated)
dom/tests/mochitest/general/test_performance_now.html
Thu, 22 Jan 2015 13:21:57 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Thu, 22 Jan 2015 13:21:57 +0100
- branch
- TOR_BUG_9701
- changeset 15
- b8a032363ba2
- permissions
- -rw-r--r--
Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6
| michael@0 | 1 | <!DOCTYPE HTML> |
| michael@0 | 2 | <html> |
| michael@0 | 3 | <head> |
| michael@0 | 4 | <title>Test for High Resolution Timer</title> |
| michael@0 | 5 | <script type="text/javascript" src="/MochiKit/MochiKit.js"></script> |
| michael@0 | 6 | <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script> |
| michael@0 | 7 | <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" /> |
| michael@0 | 8 | </head> |
| michael@0 | 9 | <body> |
| michael@0 | 10 | <script> |
| michael@0 | 11 | ok(window.performance, "Performance object should exist."); |
| michael@0 | 12 | ok(typeof window.performance.now == 'function', "Performance object should have a 'now' method."); |
| michael@0 | 13 | var n = window.performance.now(), d = Date.now(); |
| michael@0 | 14 | ok(n >= 0, "The value of now() should be equal to or greater than 0."); |
| michael@0 | 15 | ok(window.performance.now() >= n, "The value of now() should monotonically increase."); |
| michael@0 | 16 | SimpleTest.waitForExplicitFinish(); |
| michael@0 | 17 | |
| michael@0 | 18 | // The spec says performance.now() should have micro-second resolution, but allows 1ms if the platform doesn't support it. |
| michael@0 | 19 | // Our implementation does provide micro-second resolution, except for windows XP combined with some HW properties |
| michael@0 | 20 | // where we can't use QueryPerformanceCounters (see comments at mozilla-central/xpcom/ds/TimeStamp_windows.cpp). |
| michael@0 | 21 | // This XP-low-res case results in about 15ms resolutions, and can be identified when perf.now() returns only integers. |
| michael@0 | 22 | // |
| michael@0 | 23 | // Since setTimeout might return too early/late, our goal is that perf.now() changed within 2ms |
| michael@0 | 24 | // (or 25ms for XP-low-res), rather than specific number of setTimeout(N) invocations. |
| michael@0 | 25 | // See bug 749894 (intermittent failures of this test) |
| michael@0 | 26 | var platformPossiblyLowRes = navigator.oscpu.indexOf("Windows NT 5.1") == 0; // XP only |
| michael@0 | 27 | var allInts = (n % 1) == 0; // Indicator of limited HW resolution. |
| michael@0 | 28 | var checks = 0; |
| michael@0 | 29 | |
| michael@0 | 30 | function checkAfterTimeout() { |
| michael@0 | 31 | checks++; |
| michael@0 | 32 | var d2 = Date.now(); |
| michael@0 | 33 | var n2 = window.performance.now(); |
| michael@0 | 34 | |
| michael@0 | 35 | allInts = allInts && (n2 % 1) == 0; |
| michael@0 | 36 | var lowResCounter = platformPossiblyLowRes && allInts; |
| michael@0 | 37 | |
| michael@0 | 38 | if ( n2 == n && checks < 50 && // 50 is just a failsafe. Our real goals are 2ms or 25ms. |
| michael@0 | 39 | ( (d2 - d) < 2 // The spec allows 1ms resolution. We allow up to measured 2ms to ellapse. |
| michael@0 | 40 | || |
| michael@0 | 41 | lowResCounter && |
| michael@0 | 42 | (d2 - d) < 25 |
| michael@0 | 43 | ) |
| michael@0 | 44 | ) { |
| michael@0 | 45 | setTimeout(checkAfterTimeout, 1); |
| michael@0 | 46 | return; |
| michael@0 | 47 | } |
| michael@0 | 48 | |
| michael@0 | 49 | // Loose spec: 1ms resolution, or 15ms resolution for the XP-low-res case. |
| michael@0 | 50 | // We shouldn't test that dt is actually within 2/25ms since the iterations break if it isn't, and timeout could be late. |
| michael@0 | 51 | ok(n2 > n, "Loose - the value of now() should increase within 2ms (or 25ms if low-res counter) (delta now(): " + (n2 - n) + " ms)."); |
| michael@0 | 52 | |
| michael@0 | 53 | // Strict spec: if it's not the XP-low-res case, while the spec allows 1ms resolution, it prefers microseconds, which we provide. |
| michael@0 | 54 | // Since the fastest setTimeout return which I observed was ~500 microseconds, a microseconds counter should change in 1 iteretion. |
| michael@0 | 55 | ok(n2 > n && (lowResCounter || checks == 1), |
| michael@0 | 56 | "Strict - [if high-res counter] the value of now() should increase after one setTimeout (hi-res: " + (!lowResCounter) + |
| michael@0 | 57 | ", iters: " + checks + |
| michael@0 | 58 | ", dt: " + (d2 - d) + |
| michael@0 | 59 | ", now(): " + n2 + ")."); |
| michael@0 | 60 | SimpleTest.finish(); |
| michael@0 | 61 | }; |
| michael@0 | 62 | setTimeout(checkAfterTimeout, 1); |
| michael@0 | 63 | </script> |
| michael@0 | 64 | </body> |
| michael@0 | 65 | </html> |
